The proposed research will continue an analysis of the neurophysiological effects of estrogens on brainstem and diencephalic neuronal systems mediating female sexual behavior in the cat. The basic approach will be to record single unit responses in the brainstem and diencephalon to sexually relevant genital and somatic stimuli in estrous and anestrous animals. The neural mechanisms of the female cat's estrogen-dependent behavioral reponses to genital stimulation, including the estrous cry and after-reaction will be of principal interest. In addition to the electrophysiological research, neuroanatomical methods will be used to analyze the brainstem neural circuitry mediating estrogen effects on the estrous cry and after-reaction responses. The research is intended to delineate, at the level of neuronal activity, the mechanisms through which estrogens modify behavioral responses to sensory stimuli. The findings should also provide further insight into the funcitonal organization of the brainstem and mechanisms of hypothalamic modulation of brainstem function.